Technical Field
The present invention relates to compounds for organic electric elements, organic electric elements comprising the same, and electronic devices thereof.
Background Art
In general, an organic light emitting phenomenon refers to a phenomenon in which electric energy is converted into light energy of an organic material. An organic electric element utilizing the organic light emitting phenomenon usually has a structure including an anode, a cathode, and an organic material layer interposed therebetween. In many cases, the organic material layer has a multi-layered structure having respectively different materials in order to improve efficiency and stability of an organic electric element, and for example, may include a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, or the like.
Materials used as an organic material layer in an organic electric element may be classified into a light emitting material and a charge transport material, for example, a hole injection material, a hole transport material, an electron transport material, an electron injection material, and the like according to its function.
Currently, the power consumption is required more and more as size of display becomes larger and larger in the portable display market. Therefore, the power consumption is a very important factor in the portable display with a limited power source of the battery, and the situation is such that efficiency and life span issue also must be solved.
Efficiency, life span, driving voltage, and the like are correlated with each other. For example, if efficiency is increased, then driving voltage is relatively lowered, and the crystallization of an organic material due to Joule heating generated during operation is reduced as driving voltage is lowered, as a result of which life span shows a tendency to increase. However, efficiency cannot be maximized only by simply improving the organic material layer. This is because long life span and high efficiency can be simultaneously achieved when an optimal combination of energy levels and T1 values, inherent material properties (mobility, interfacial properties, etc.), and the like among the respective layers included in the organic material layer is given.
In order to solve the problem of luminescence in the hole transport layer in recent organic electroluminescent devices, an emission-auxiliary layer must be present between the hole transport layer and the light emitting layer, and it is time to develop different emission-auxiliary layers according to respective light emitting layers (R, G, B).
In general, an electron transferred from an electron transport layer to a light emitting layer and a hole transferred from a hole transport layer to the light emitting layer are recombined to form an exciton. However, it mainly has a low T1 value since a material used in a hole transporting layer should have a low HOMO value. Due to this, excitons generated from a light emitting layer are transported to the hole transporting layer, resulting in a charge unbalance in the light emitting layer. Thus, light emission occurs in the hole transporting layer or at an interface of the hole transporting layer so that the organic electroluminescent device is reduced in color purity, efficiency, and lifespan.
In addition, when a material having a rapid hole mobility is used to make a low driving voltage, the efficiency tends to decrease. This is because, in a general organic electroluminescent device, hole mobility is faster than electron mobility, which leads to charge unbalance in the light emitting layer, resulting in reduction in efficiency and lifetime.
Therefore, the emission-auxiliary layer should be formed of a material having hole mobility, lei h electron block (I), and wide band gap so as to have a proper driving voltage capable of solving the problems of the hole transport layer.
These requirements are not met by the structural properties of the core of the emission-auxiliary layer material alone, but are achieved when the properties of the material, such as core and sub-substituent, are all properly combined. Therefore, in order to improve the efficiency and lifetime of an organic electric device, it is strongly required to develop materials of the emission-auxiliary layer having a high T1 value and a wide band gap.
That is, in order to allow an organic electric element to fully exhibit the excellent features, it should be preceded that the materials consisting an organic material layer of the element, for example, a hole injection material, a hole transport material, a light emitting material, an electron transport material, an electron injection material, an emission-auxiliary layer material or the like, are supported by a stable and efficient material. However, such a stable and efficient material of organic material layer for an organic electric element has not yet been fully developed. Accordingly, there is a continuous need to develop new materials for an organic material layer, particularly, it is strongly required to develop materials of the emission-auxiliary layer and/or materials of the hole transport layer and the light emitting layer.